Histology of the ligamentum flavum in patients with degenerative lumbar spinal stenosis

The degree of calcification as well as the structural changes of the elasti c fibres in the ligamentum flavum in patients with degenerative lumbar spin al stenosis were evaluated and the results were compared to those of patien ts without spinal stenosis. In 21 patients (13 male, 8 female) with lumbar spinal stenosis the ligamentum flavum was removed, histologically processed and stained. The calcification, the elastic/collagenous fibre ratio as wel l as the configuration of the fibres were evaluated with an image analyzing computer. As a control group, 20 ligaments of 10 human corpses were proces sed in the same way. The results were statistically analysed using the Mann -Whitney-Wilcoxon test (alpha = 0.05) and the t-test (alpha = 0.05). Nearly all the ligaments of patients with lumbar spinal stenosis were calcified ( average 0.17%, maximum 3.8%) and showed relevant fibrosis with decreased el astic/collagenous fibre ratio. There was a significant correlation between age and histological changes (P < 0.05). In the control group we only found minimal calcification in 3 of 20 segments (average 0.015%). No relevant fi brosis was found and the configuration of elastic fibres: showed no patholo gic changes. The results of this study illustrate the important role of his tological changes of the ligamentum flavum for the aetiology of lumbar spin al stenosis.